ST. PIERRE-JOLYS, Man. - Several thousand people in southern Manitoba have been told that a pipeline explosion could mean they'll be without natural gas service for up to several days as temperatures hover close to —20 C.

"As far as the temperature is concerned, the words 'polar vortex' is what they're saying," Myron Dyck, a spokesman for the Town of Niverville, said on Saturday.

The explosion and fire at a TransCanada Pipelines valve site near St. Pierre-Jolys happened early Saturday morning, sending a massive fireball into the dark sky.

The flames were out by Saturday afternoon and there were no reported injuries.

But Manitoba Hydro said that in order to repair the line, TransCanada shut off its supply of natural gas for several municipalities affecting approximately 4,000 people.

The utility said it had no estimate from TransCanada about when service would be restored and that customers should prepare for the outage to last at least one day.

The temperature in Niverville on Saturday afternoon was —18 C and Environment Canada was calling for even colder temperatures on Sunday and Monday.

Dyck said people in the region use either gas and gas or electricity to heat their homes.

"We have contingency plans in place should this be for a greater time period," Dyck said when asked about what actions the town might take to assist residents without heat.

In the Rural Municipality of Hanover, a warming centre was being set up in a local church.

"For those who feel the need to leave their homes, we urge people to stay with friends or family with an alternative heat source," Hanover Emergency Coordinator Denis Vassart said on the community's website.

A Manitoba government spokesman said it wasn't known how many people had alternative heat sources such as space heaters or fireplaces.

TransCanada said it shut down the Emerson Lateral portion of the Canadian Mainline natural gas pipeline system due to the explosion and vented the remaining gas. It said trucks containing compressed natural gas were being sent to metering stations to provide gas to some critical services such as personal care homes and hospitals, as well as schools or churches being used as emergency warming centres.

TransCanada said in a news release that was working with Manitoba Hydro to restore regular natural gas service as quickly as possible.

Niverville Deputy Mayor John Funk said in a statement on the town's website that depending on the extent of the repairs, service is expected to be lost for minimum of 24 hours to multiple days.

Funk said Manitoba Hydro is asking residents to turn down thermostats and minimize use of electric heaters. He also urged caution when using all types of space heaters, and warned people not to use barbecues or any other unapproved heaters indoors that might produce carbon monoxide.

Five homes were evacuated as a result of the explosion and roads leading into the site were closed.

The Transportation Safety Board of Canada and the National Energy Board are investigating.